The present invention relates to electrical circuit breakers including motor controllers and, in particular, to a lockout preventing unauthorized activation of a circuit breaker or motor controller.
Safety practice requires that electrically powered machines be isolated from power before adjustment, maintenance, or repair of the machine by a human operator. Such isolation must be done in a manner to prevent accidental reconnection.
This isolation may be accomplished by opening the circuit breaker associated with the machine and locking the circuit breaker toggle in the xe2x80x9coffxe2x80x9d position using a xe2x80x9csealedxe2x80x9d wire connection or a padlock and a special locking fixture. As used herein, the term xe2x80x9ccircuit breakerxe2x80x9d should be considered to include manual motor controllers and the like.
Referring to FIG. 1, a prior art single-pole, miniature-style circuit breaker 10, includes a front escutcheon plate 12 having an outer edge 14 and an opening 16 therein through which a toggle operator 18 extends. The toggle operator 18 pivots in a longitudinal direction 20 between a downward OFF position 22 (as shown in FIG. 1), and an upward ON position 24. A free end of the toggle operator 18 is attached to a transversely extending bar toggle 26 that may be easily operated by a person""s finger.
Referring also to FIG. 2, a prior art lockout 30 for such a circuit breaker 10 uses an aluminum extrusion having a transversely extending channel 32 with opposed lower wall 34 and upper wall 36. The channel 32 is sized to receive the toggle bar 26 when it is in the OFF position. A set screw 38 passes through the upper wall 36 into the channel 32 so that the toggle bar 26 may be captured between a tooth 40 projecting inward from lower wall 34 and a pointed tip of the set screw 38.
The upper wall 36 attaches to a foot 42 which abuts the escutcheon plate 12 at a front upper edge 14 of escutcheon plate 12. In this way, motion of the toggle bar 26 in an upward arc along the longitudinal axis 20, such as would tip the lockout 30, is resisted by pressure of the foot 42 against the front surface of the escutcheon plate 12. As shown in the drawing, for some circuit breakers 10, the foot 42 of the lockout 30 is very close to the edge 14 of the escutcheon plate 12 and may slip over that edge 14 allowing activation of the circuit breaker 10 despite the lockout 30.
The head 46 of the set screw 38 extends into an opening of an eye 44 attached generally to the upper wall 36 and providing a cylindrical transverse aperture. An access hole 48 in the wall of the eye 44, opposite the head 46 of the set screw 38, allows insertion of a screwdriver blade 50 to engage the head 46 for tightening the set screw 38 against the toggle bar 26 or loosening it therefrom.
Referring also to FIG. 3, a shackle 52 of a padlock may be inserted through the eye 44 to block access by the screwdriver blade 50 to the head 46 of the set screw 38. Generally, the shackle 52 must be somewhat smaller than the diameter of the eye 44 because of the protrusion of the head 46 into the aperture of the eye 44. The transverse extending eye 44 requires that the shackle 52 be positioned so that the case 54 of the padlock lies across adjacent circuit breakers 10xe2x80x2 and 10xe2x80x3 interfering with operation of these circuit breakers 10xe2x80x2 and 10xe2x80x3 and preventing the use of a second lockout on these adjacent circuit breakers 10xe2x80x2 and 10xe2x80x3.
The present invention provides a mechanical lockout also engaging a toggle bar of a circuit breaker but in which the eye is positioned to allow a padlock used with the lockout to hang edgewise. This change in the orientation of the padlock reduces or eliminates interference between the padlock and adjacent circuit breakers and/or lockouts on those circuit breakers. An improved foot on the lockout includes a heel engaging an aperture of the escutcheon plate of the circuit breaker preventing slippage of the lockout with movement of the toggle bar of the circuit breaker. The set screw of the lockout is further mounted in a counter bore below the surface of the eye allowing proportionally larger shackled locks and improved tamper resistance.
More specifically, the present invention provides a lockout for a circuit breaker having a toggle operator switchable between an ON and OFF position. The lockout includes a transverse channel having opposed first and second walls for receiving the toggle operator therebetween, the first wall including a hole extending therethrough. A screw fitting within the hole can be extended toward the second wall by rotation of the screw to clamp the toggle operator within the channel. A foot attached to the channel engages a portion of the circuit breaker, other than the toggle operator, to resist switching of the toggle operator when the toggle operator is clamped in the channel. A longitudinal eye is attached to the first wall to receive a padlock shackle along a direction substantially perpendicular to the channel so that the shackle blocks access to the head of the screw.
Thus, it is one object of the invention to provide an improved orientation of the eye of a lockout allowing adjacent circuit breakers to be operated or to be locked out without interference from the padlock.
The screw may be a set screw having its head positioned within a counter bore of the hole so that the received shackle covers the counter bore.
Thus it is another object of the invention to eliminate access to the head of the set screw and to allow the use of a larger diameter shackle associated with commonly available padlocks and/or to reduce the necessary size of the eye.
The hole may open into the longitudinal eye.
Thus, it is another object of the invention to prevent movement of the shackle within the eye from allowing access to the set screw.
The toggle of the circuit breaker may extend from an opening in an escutcheon plate and the foot may include a heel portion fitting within the opening.
Thus, it is another object of the invention to provide a more positive lockout that cannot be defeated by a sliding of the lockout mechanism along the surface of the escutcheon plate.
The foot may also include a toe fitting over the outer edge of the escutcheon plate.
Thus it is another object of the invention to provide a positive indication of a proper fitting of the lockout to the circuit breaker that may indicate that the lockout is not being used on the toggle when the toggle is in the OFF position as is desired.
The eye may be oriented so that the shackle of the padlock is substantially vertical when the circuit breaker is mounted so that the toggle operator is switched in a vertical direction.
Thus, it is another object of the invention to allow the padlocks to hang stably without gravitationally induced twisting and interference.
The channel may fully cover the toggle operator when the toggle operator is positioned within the channel.
Thus, it is another object of the invention to better enclose the toggle to reduce tampering and removal of the operator by twisting.
Alternatively, the channel may extend at least two times the length of the toggle operator to engage toggle operators of adjacent circuit breakers.
It is thus another object of the invention to provide the ability to lockout multiple adjacent circuit breakers.
These particular features, objects and advantages may apply to only some embodiments falling within the claims and thus do not define the scope of the invention.